The administration of medicaments by inhalation is one of the most promising approaches in therapy that can be applied to a wide variety of diseases. The first inhaled medicaments were used for the treatment of diseases affecting the airways; however there has been an increased interest recently for the development of inhaled forms of medicaments that target various other diseases, such as diabetes.
The administration of medicaments by inhalation is carried out by using inhalation devices (inhalers). A large number of such devices are comprised in the state of the art. A large category of inhalers includes those wherein the medicament is situated in a receptacle in the form of dry powder and wherein the patient, by using the power of his/hers lungs, creates a streaming of air which carries along the powder which is subsequently inhaled through a mouthpiece. These devices are known as dry powder inhalers (DPIs). The powder in said devices is either situated in a container from where the required amount is measured using an internal mechanism, or it is packed as individual doses in the corresponding receptacles such as blister packs or capsules. The powder comprises the active ingredient which in most cases is combined with one or more excipients.
International patent application WO03082389 discloses a dry powder inhaler wherein the medicament is stored in the blisters of specially designed single dose blister strips. The device comprises a mouthpiece, a blister strip support surface and a strip storage compartment. The strip support surface comprises an attachment point (e.g. a protrusion), a cavity which receives the blister of the strip and guides for the correct alignment and firm placement of the strip. The mouthpiece is movably joined to the support surface in such a way that when the blister strip is placed on the support surface and the mouthpiece is in its basic position, the base of the mouthpiece touches the strip and covers completely the powder containing blister.
The mouthpiece of said device is comprised of three parts, an exterior part and two interior parts of conical shape. The first of the interior parts, whose lower side has two openings and touches the blister of the strip, is divided into two chambers through which the air which enters the mouthpiece carries the powder. Then, the mixture of air and powder passes through the second interior part of the mouthpiece and exits the device.
Although the mouthpiece of the above mentioned device functions satisfactorily, there are some points which could be improved. First, due to the design of the mouthpiece, the resistance of the device is pretty high. The resistance of the device corresponds to the force with which the patient has to inhale in order to receive the medicament. It is desirable that the resistance of the device is not very high, so that the device may be used by a wide variety of patients. Furthermore, when the above device is used, a small amount of powder is accumulated in the interior wall of the mouthpiece. Although the amount powder is so small that the therapeutic efficacy of the device is not affected, this accumulation may create problems after long use since in such cases the device would have to be cleaned.
The present invention solves the above-mentioned problems since on the one hand it provides the possibility of reducing the resistance of the device, and on the other it eliminates the possibility of powder accumulation in the interior of the mouthpiece.